A combined cycle power generation plant comprising of a combination of a gas turbine and a heat recovery boiler has a power generation efficiency higher than that of other thermal power generation plants, it mainly uses natural gas as a fuel, and it has less production of sulfur oxide and ash dust, so that its exhaust gas purification load is small, for which it has attracted a lot of attention as a successful power generation system. In addition, a combined cycle power generation plant is excellent in load responsiveness since it can quickly change its power generation output according to power demand, and its startup time is comparatively short (it rises quickly), so that it has attracted attention as a power generation method suitable for peaking operation (daily start daily stop) with starts and stops made according to daily power demand cycles.
A combined cycle power generation plant comprises of a power generating gas turbine, a heat recovery boiler that generates steam by using exhaust gas of the gas turbine, and a steam turbine that generates power by using steam obtained by the heat recovery boiler.
FIG. 1 is a schemic view of a horizontal heat recovery boiler equipped with a supplementary firing burner inside. The heat recovery boiler has a casing 1 as a gas duct in which an exhaust gas G from the gas turbine flows horizontally. A supplementary firing burner 2 is located inside the casing 1 in the vicinity of the inlet into which the gas turbine exhaust gas is led, and a number of heat exchanger tubes are located inside the casing 1. The casing 1 is supported by structural members mainly consisting of main columns 33 and main beams 34.
In comparison to components that form conventional high-capacity thermal power generation plants that generate power by burning fossil fuels such as coal, petroleum, or natural gas, etc., the components of a combined cycle power plant including a heat recovery boiler are smaller in capacity and transportable only by sea after being assembled to a nearly completed state in a component manufacturing factory. When the construction site is relatively near the manufacturing factory and near the sea, the installation at the construction site is comparatively easily performed as described above. Therefore, the installation can be completed in shorter time than in the case of high-capacity components of thermal power generation plants.
However, in combined cycle power generation, power generation efficiency higher than the conventional is required. Also required is a high-speed startup and stop operation. Hence the heat recovery boiler is made out of a large number of components, and when the conditions of the construction site are different from the above-mentioned conditions and the degree of completion in the factory is low, its installation requires great labor and time. For example, for a heat recovery boiler, a group of approximately one-hundred heat exchanger tubes and its header are set as one unit and are transported to the construction site, and the heat exchanger tube bundle panels are hung down on a unit basis from structural members (main frames) including the main columns 33 and the main beams 34 of the heat recovery boiler which have been constructed in advance at the construction site with intermediate beams located on the ceiling wall of the casing 1 supported by the structural members. Repetition of such operations of hanging and installing the one-hundred heat exchanger tube bundle panels results in an increase of operations at high elevations and it carries increased safety risks. In addition, the construction period is longer, and the construction costs are higher.
Therefore, by considering transportation and installation of the heat exchanger tube bundle panels 23 of the heat recovery boiler, a technical development has been earnestly demanded which makes the heat recovery boiler construction easy by fabricating modules, wherein a number of heat exchanger tube bundle panels 23 are defined as one block (hereinafter, referred to as a heat exchanger tube bundle panel module). The entire heat recovery boiler is divided into several modules and the modules are completed as one unit within the component manufacturing factory. Installation is completed by assembling the modules at the construction site.
Particularly, when considering that it is difficult to obtain the heat recovery boiler construction parts and secure skilled personnel necessary for construction outside Japan, the module construction method is very effective. The components are completed as partial products divided into a number of modules in the factory in Japan. Quality control or process control systems are adequate and many skilled workers are available in Japan. The modules are transported to the construction site to possibly minimize the operations at the construction site where they are assembled.
The method in which the entire heat recovery boiler is manufactured by dividing it into several modules within the factory and then assembled at the construction site is known by, for example, U.S. Pat. No. 859,550 (Patent family: Japanese Published Unexamined Patent Application No. S62-266301). The U.S. Pat. No. 859,550 discloses a construction method in which modules of heat exchanger tube bundle panels are protected by being housed in a frame body formed of a rigid member when they are transported, and the frame body can be used as it is as a main frame of the heat recovery boiler at the construction site.
[Patent Document 1] U.S. Pat. No. 859,550
[Patent Document 2] Japanese Published Unexamined Patent Application No. S62-266301